I just installed ubuntu and I really like it, even though the dual-boot configuration took me at least 2 days :p

My dual-boot works fine, except for the fact my windows doesn't boot if one of my external drives is already connected?

Here is my setup:
I have an SSD for booting that i split (100gb for windows, 25gb for ubuntu), and I dual-drive with an HDD that I use for storage. I have an uefi-bios and 64x I7 cpu, 16gb ram.

I have 2 external HDD's (for video and back-ups) that I allmost never disconnect.

If I come out GRUB, I can get into ubuntu without any trouble of my ext-HDD.
But when I select my win7 and 1 of my HDD's is connected with 1 of my usb-ports, I get a black screen with a text-cursor. I can't type or do anything, only hard reset.

I re-installed my usb-ports, searched for hidden boot.ini in my HDD's, checked my boot-order in BIOS, but nothing works. So the only option is something with GRUB i think?
Is there a way to make changes to my usb-boot? Or does anyone now what is holding my windows from booting?

Keep in mind that there is absolutely no problem booting windows if ext-HDD is not connected?

Hope you guys can help me, because I know nothing about ubuntu and GRUB :D